The present invention refers to a device for determining the extent to which a container is full, in particular with a liquid, the device having a membrane with one side facing the fluid to be measured. On the other side of the membrane is an electromechanical transducer which induces vibrations in the membrane. The invention furthermore concerns a container configured for such a device.
Such devices are employed, as a rule, in automobile tanks in order to be able to produce a warning signal when a minimum fluid level is reached. The action of these devices is based on the fact that the vibrations of the membrane are damped by the liquid which acts on it. The different vibratory behavior in the presence and absence of liquid is detected in an evaluation device so that the desired warning signal can be produced.
In automobile gasoline tanks as well as in other containers, a problem arises in that upon the introduction of liquid, particularly upon the initial filling, a relatively large amount of air and gas passes into the liquid. Gas or air bubbles can then attach themselves to the side of the membrane facing the liquid, with the result that the membrane can vibrate more easily than if it were completely covered by the liquid. A false warning is then easily the result.